Save With Replace; Verifying Programs - Commodore 1541 User Manual

SA VE WITH REPLACE OPTION If
the disk
cop.~ 0 ~
the
pr~gram
differs even a tiny bit from the copy in memory ,
•VERIFY
ER~OR
wil!
be
d1 spla~ed ,
to tell you that the copies differ. This in itself
oesn'I mean either copy 1 s bad , but 1f they were supposed to be identical , one or the other
If
a file already exists , it can'
t be saved again because the disk ~nly allows o~e c~as a
problem . , . . .
of any given file name per diskette. It is possible to get around this problem using q Naturally ' there
~
no point in trying to verify a disk copy of a program after the
Rename and Scratch commands described later. However, if all you wish to do is repJ ·ginal is no longer in memory . With nothing to compare to ,
an
apparent error will
a program or data file with a revised version , another command is more convenieqways be
announ~ed ,
even though the disk copy is always and automatically verified as it
Known as Save-with-replace , or @ Save, this option tells the disk to replace any file, Wfitten to the disk .
finds in the directofy with the same name , substituting the new file for it.
oRMAT FOR THE VERIFY COMMAND :
FORMAT FOR SA VE WITH REPLACE: FORMAT FOR SA VE
WITH
REPLAQ
BASIC 2 BASIC 3.5 VERIFY "drive # :pattern " ,device# , re!ocate flag
SAVE "@Drive # :file name", device# DSAVE " @ file name " , Ddri ve
1
Udevice # here '_'drive # :" is an optional drive number (0 on the 1541,) " pattern " is any string
1
press1on that evaluates to a file name, with or without pattern-matching characters and
where all the parameters are as usual except for adding _ a leading _ " at'_' sign_(@. ) 7 device #" is the disk
devi~e
number, normally
8. If
the relocate flag is presen; and
" O:"
in the Basic 2 version
, though a holdover from earlier dual drives is
required h
uals l, the file will be venfied where originally saved , rather than relocated into the
a
ic text area.
EXAMPLES :
useful alternate form of the command is:
SAVE" @O:REVISED PROGRAM"
,8
DSAVE "@REVISED PROGRAM "
VERIFY "* '',device#
The actual procedure is that the new version is saved completely , then the old veru
is scratched , and its directory entry altered to point to the new version . Because it w verifies the last file used without having to type its name or drive number. However it
this way , there is little , if any , danger that a disaster such as having the power goingon't work properly after save-with-replace , because the last file used was the dne
midway through the process would destroy both the old and new copies of the leted,_ and the drive will try to compare the deleted file to the program in memory . No
Nothing happens to the old copy until after the new copy is saved properly· .
~will ~suit,
but ' ' VERIFY ERROR ' ' will always be announced. To use verify after
However, we do offer one caution-<lo not use @ Save on an almost-full disk AVE, include at least part of the file name that is to be verified in the pattern .
Only use it when you have enough room on the diskette to hold a second complete cop ,
One
other note about Verify-when you Verify a relocated file , an error will nearly
the program being replaced . Due to the way @ Save works , both the old and new vernways_
be
announced, due to changes in the link pointers of Basic programs made during
of the file
are
on disk simultaneously at one point, as a way of safeguarding against
IOlloc~tion.
It is
best to only verify files saved from the same type of machine and
the program . If there is not enough room left on diskette to hold that second copy ,
onJt~tical m~mory
size. For example , a Basic program saved from a VIC 20 can' t easlly be
much of the new version will be saved on the 1541 as there is still room for.
Afteinfi~
using a Commodore 64, even when the program would work fine on both
command completes , a look at a directory will
~how
the new version is
present,~~~s_ (unless
the
progr~
is re-saved). This shouldn't matter, as the only time you'll
doesn't occupy enough blocks to match the copy in memory . Unfortunately • the V _ Ymg files on machines other than the one which wrote them is when you are
command (see next section) will not detect this problem , because however much
dil".1f~ng
two disk files to see if they
are
the same . This is done by loading one and
n Ymg
a · h
saved will have been saved properly . :rno . gamst t e other, and as suggested , can only be done on the same machine and
ry
size as the one on which the files were first created .
VERIFYING PROGRAMS
L <\SING OLD PROGRAMS: BASIC 2
Although not as necessary with a disk drive as with a cassette, Basic's Vf
Sc
command can be used to make doubly certain that a program file was properly sav Upi:tch command allows you to erase unwanted files, and free the space they
disk .• It works much like the. Load
com~and,
except
tha~
it only
compai;esJC Via for use by oth_ e r files. It can be used to erase either a single file , or several files at
character in the program agamst the equivalent character m the computer s pattern-matching .
ory, instead of actually being copied into memory.
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